1. Field of the Invention
The present invention relates to a fuel cell stack, and particularly to a waterproof structure that surrounds terminals used for voltage measurement in each cell.
Priority is claimed on Japanese Patent Application No. 2004-76448, filed Mar. 17, 2004, and No. 2004-200312, filed Jul. 7, 2004, the contents of which are incorporated herein by reference.
2. Description of Related Art
Among fuel cells that are mounted in a fuel cell vehicle or the like, there are those in which a solid polymer electrolyte membrane is sandwiched between an anode electrode and a cathode electrode so as to form a membrane electrode structure. This membrane electrode structure is sandwiched between a pair of separators so as to form a cell (i.e., a unit fuel cell). In this type of fuel cell, typically, a plurality of cells are stacked and used as a fuel cell stack.
In this fuel cell, if fuel gas (for example, hydrogen gas) is supplied to the anode electrode and oxidizing gas (for example, air that contains oxygen) is supplied to the cathode electrode, then the hydrogen gas is ionized at the anode electrode, and moves into the solid polymer electrolyte membrane. Electrons then pass through an external load and move into the cathode electrode, where they react with oxygen to create water. Electrical energy can be extracted from this series of electrochemical reactions.
In this type of fuel cell, in order to determine whether or not each cell is in a normal state when in operation, the voltage between separators that constitute each cell (referred to below as the cell voltage) is measured, and the power generating state of each cell is controlled.
As is described, for example, in Japanese Patent Application Unexamined Publication No. 11-339828, a conventional technique is known for connecting lead wires, which are connected to a cell voltage detection circuit, to the separators that employs a structure in which a socket shaped connector that is provided at a distal end of the lead wires is inserted into terminals formed in the separators.
In a fuel cell, in order to avoid short-circuiting between cells that is caused by water entering from the outside, it is necessary for waterproofing treatment to be performed around the terminals. However, providing an individual waterproofing member for each of the large number of terminals that is equal to the number of stacked separators is extremely complicated and gives rise to poor productivity.
Therefore, the present invention provides a fuel cell stack that enables a terminal group made up of a plurality of terminals to be waterproofed all together without a waterproofing member needing to be provided individually for each terminal, and that has a waterproofing mechanism with excellent sealing properties.